Staphylococcus aureus, a gram-positive bacterium, is one of the leading causes of hospital- and community-acquired infections in developed countries. It is estimated that S. aureus is commensally associated with skin, skin glands and mucous membranes of 20-30% of the human population. S. aureus can cause infection of the bloodstream, lower respiratory track, skin and soft tissue, leading to bacteremia, pneumonia, endocarditis and osteomyelitis. Initially, S. aureus infections could be successfully treated with β-lactam antibiotics, like penicillin and methicillin. However, by the mid-1900s, the emergence of resistant strains of S aureus had been reported, including methicillin-resistant S. aureus (MRSA) which has become endemic in many hospitals worldwide. Kirby, W. M., Science 99, 452-3 (1944). In addition to β-lactam antibiotics, S. aureus has also developed resistance to several other classes of antibiotics, including aminoglycosides, macrolides, lincosamides, chloramphenicol, sulfonamides, streptomycin and tetracycline. Schito, G. C., Cli. Microbiol Infect 12 Suppl 1, 3-8 (2006). The capability of S. aureus to resist multiple antibiotics has rendered its treatment difficult, leading to a higher mortality in patients. Thus, development of new antibacterial agents effective against S. aureus, especially strains resistant to multiple antibiotics, has become an urgent public health issue.